Video chunking can be described as the process of splitting up a video into a number of chunks or smaller videos, where each chunk represents a specific non-overlapping time block of the video. For example, each chunk may represent five seconds of the video. When a client wants to receive the video it requests the chunks using a standard protocol, such as HTTP (Hypertext Transfer Protocol). The client requests the chunks in the proper order and feeds the data to a decoder to provide a smooth flowing video.
Video chunking has recently been used to implement adaptive streaming of video. Specifically, several versions of a video are created, each representing a different video quality (and thus bandwidth). Each of these files is then split up into a number of chunks or smaller videos. This allows the client to select which chunk to download based on the current available bandwidth and/or the depth of the buffer. For example, the client may select a chunk from the lowest quality version of the video when there is limited bandwidth. When the bandwidth improves or increases the client may then switch to chunks from a higher quality version of the video. In this manner, the video stream can be dynamically adapted to the available bandwidth.
Two exemplary adaptive video chunking implementations are the Move Networks™ implementation and the Microsoft™ implementation. In the Move Networks™ implementation, one file is created for each chunk. Therefore each file represents a specific time frame and a specific bandwidth or quality. One problem with this particular implementation, however, is the large number of files that need to be created and managed. For example, if ten versions of a ten-minute video are created, and each version of the video is divided into two-second chunks, there will be 3000 chunks and thus 3000 separate files.
In the Microsoft™ implementation, referred to as Microsoft Smooth HD™, only one file is created for each bandwidth and ISO (International Organization for Standardization) MP4 (Moving Picture Expert Group-4) movie fragments (MOOF) are used to divide each file into chunks. The client then creates a HTTP URL (Uniform Resource Locator) that indicates the time period and the bandwidth (quality level) that it wishes to receive. A Microsoft IIS (Internet Information Services) server parses the request and retrieves the correct MOOF from the correct file.
The Microsoft™ implementation significantly reduces the number of files over the Move Networks™ implementation since there is only one file per bandwidth (quality) as opposed to one file per bandwidth per time period. However, the Microsoft™ implementation still requires multiple files per video. In addition, the Microsoft™ implementation demands an intelligent server that can parse the HTTP URL and retrieve the correct MOOF from the correct file.
Recently, a new video coding standard, referred to as Scalable Video Coding (SVC) was developed. SVC is an extension of the H.264/MPEG-4 AVC video compression standard. When a video file is SVC encoded, it is encoded into one or more layers, of differing quality. The layer with the lowest quality, referred to as the base layer, contains the most important part of the video stream. One or more enhancement layers may then be encoded to further refine the quality of the base layer. The enhancement layers are used for improving the spatial resolution (picture size), temporal resolution (frame rate), and the SNR (signal to noise ratio) quality of the base layer.
None of the existing adaptive video chunking implementations takes advantage of the features of SVC to optimize the encoding and file sizes.